Process of making colored sheets of cellulose esters, synthetic resins, and the like



G. J. ESSELEN ET AL 2,078,214 PROCESS OF MAKING COLORED SHEETS OFCELLULOSE 7 April 20, 1937.

ESTERS. SYNTHETIC RESINS, AND THE LIKE Filed June 17, 1 935 [/2 06/2tors W Patented Apr. 20, 1937 UNITED STATES PATENT OFFICE PROCESS OFMAKING COLORED SHEETS OF CELLULOSE ESTERS, SYNTHETIC RESINS, AND THE'LIKE Application June 17,

1 Claim.

The present invention relates to a novel process of making sheets or aweb, ofcellulose esters, synthetic resins or like plastic materials incolors or having ornamental effects.

At the present time sheets of cellulose ester plastics or the like canbe made by a continuous process which forms a web and seasons it, but ithas not been practical to make a wide variety of colors and shades ofstock in this way since 10 the process is economical only for largebatches which provide long runs .and do not require frequent cleaning ofthe machines. Only small quantities of any particular color areordinarily required, but many colors, and shades are neces- 15 sary.Accordingly, colored sheet stock has heretofore been made entirely bythe cake or block process, in accordance with which a cake or block isformed, is then sliced into sheets and the seasoning of the sheetscompleted. This process.

is exceedingly slow and expensive. Our novel process makes it possibleto produce colored sheet stock by a continuous process and withoutresorting to the cake process and at much less expense.

In accordance with the novel process, we make by the continuous processa transparent, translucent or white opaque sheet orweb from celluloseesters, synthetic resins or like plastic materials and thereafter applysimultaneously on both sides of the web a thin coating of a suitablecolored or ornamental finishing liquid. When so treated the sheet hasthe appearance of a sheet made entirely from colored stock. In additionvery beautiful effects may be obtained by choosing the colors to beapplied to the face or faces of the base material. It will be understoodthat the base material may be of any desired appearance and the surfacecoating likewise of any desired appearance, and in general in thisspecification we have used the word color to include clear transparent,white opaque and even black and have not limited it to the spectrumcolors.

The novel process greatly reduces the cost 01' colored sheet stock sincethe sheet forming machine may be run continuously to form the colorless,i. e. transparent, translucent or white opaque, base material and thismaterial may subsequently be colored or coated or ornamented as desired.

The surface coatings applied may themselves be transparent translucentor. opaque, they may.

be of a single color or a non-uniform mixture of colors, or they maycontain ornamental material 55 in suspension, as, for instance, pearlessence.

1935, Serial No. 27,012

metallic scales, and the like and the opposite sides of the sheet may begiven the same or different colors or ornamentation. Our invention,therefore, makes it possible to produce by the continuous process many,if not all, of the colored and pearl effects, either plain or mottledwhich are now produced by the cake process and thus to take advantage ofthe verygreat economies of the continuous process. Furthermore, certaineffects can be produced by our process which are not now possible withthe cake process.

The improved process consists in general in preparing a coating liquidfrom a mixture of a suitable carrier liquid, such as lacquer, and thedesired coloring matter; flowing the colored coating liquid onto a bathof suitable liquid, for instance water, to form a film of desiredthickness; then lineally passing the sheet to be coated continuouslydown through the film of coating liquid into the bath at a speed suchthat the film of coating material on each side of the sheet will bedrawn against the sheet continuously; and carrying the sheet through thebath and out of it at a place where the bath is free from the coatingfilm. In practice, it is desirable to employ a tank divided into twoparts or cells by a partition which does not extend to the bottom of thetank. In this way the coating is applied simultaneously to both sides ofthe sheet but is not injured when it is removed from the tank.

In practicing our invention, we prefer to harden somewhat the film onthe surface of the bath by removing some of the solvent contained in thecoating material just before it contacts with the sheet of basematerial. When this is done, we treat the surface of the sheet with asmall quantity of some suitable solvent or softening agent whichactivates the surface of the sheet and renders it more easily adherentto the film taken from the surface of the bath. By this treatment, whichis not claimed herein as it is made the subject of a companionapplication, a tougher film is formed and the sheet may be passedthrough the bath at substantialy greater .speed.

Referringto the'drawing, the figure is a vertical section of a machineillustrating somewhat diagrammatically our invention.

At I is shown a machine having a nozzle H for forming a continuous sheetor web I3. From the die, the web passes through suitable driers It inwhich the solvent is extracted and the stock is seasoned. The web thusformed is, for instance, of transparent cellulose ester plastic and isto be converted into a blue opaque material. The web I3 is fed lineallyby positively driven feed rollers l5 and I6 downward into the bath l1contained in the tank l8. The tank I8 is provided with a partition I 9which divides it into two cells. The partition l9 extends downward belowthe level of the bath I! in the tank, having due regard to variations inlevel which may take place. Above the entering cell, which is at theleft of the partition, we place two troughs 20 and 2| which supply thecoating material for the web. These troughs, or other suitable supplymechanism, are arranged to supply the coating material at a uniformregulatable rate. The coating material, which is preferably a suitablenitrocellulose lacquer containing the desired coloring material, floatson the surface of the bath and spreads out forming a film thereon. For.

making light blue opaque stock, this film may be made satisfactorily ofa lacquer containing 10 ounces of titanium dioxide, 1 ounce of Chineseblue in each gallon of clear lacquer. The clear lacquer is made bydissolving 1 pound of second nitrocellulose and of a pound of dibutylphthalate in 1 gallon of solvent mixture. A confactory. At 22 and 23 areshown two air nozzles which blow warm air gently on the surface of thefilm and remove some of the solvent and harden and toughenthe filmslightly as already described. If preferred, the bath may be heatedslightly. The web l3 passes lineally down through the film 24 on thesurface of the bath and the film adheres to each side of the web. As theweb or continuous sheet lineally progresses downward through the bath,the film is drawn by its own toughness and cohesion toward the sheet sothat both sides of the sheet are continuously and smoothly coated. At-25and 26 are shown spray nozzles which apply a fine mist of a suitablesolvent, for instance butyl acetate,"to the sides of the sheet after itleaves the feed rolls I5 and I6 and before it comes in contact with thefilm of coating material on the surface of the bath. After passingthrough the film, 24 of coating material on the surface of the bath theweb passes under the partition l9 and then is led upward through theright hand cell of the bath emerging at 21. There is no film of coatingmaterial on this portion of the bath. After emerging from the bath, jetsof warm air are directed by nozzles 28 and 29 against the opposite sidesof the sheet, drying and hardening the film of coating materialsufliciently so that it will not be marred by or adhere to the rollers30 and 3| over which the material is led. By giving the rollers l5 and.IG and 30 and 3| the same peripheral speeds a festoon is formed passingunder the partition and the sheet is guided through the bath withoutcoming in contact with any object from the time it leaves the feedrollers l5 and I6 until it is received by the delivery rollers 30 and3|.

What we claim is:

The improvement in the continuous process of making sheet stock fromcellulose esters, synthetic resins and the like whereby a continuous webof said material is produced which comprises supplying to a bath afloating film of colored liquid capable of adhering to the web, feedingthe web lineally through the film into the bath, thereby causing thefloating film to adhere to both .sides of the web, thereafter feedingthe coated

